Treatments with evidence of efficacy do not readily transfer into routine clinical practice. A particular challenge is changing established practice behaviors through continuing professional education. The average clinician practices for 30 years or more, during which time optimal practice is likely to undergo major changes. The usual continuing education format of a one-time workshop is unlikely to modify stable practice behavior substantially. The proposed study applies the basic design of a randomized clinical trial to test the efficacy of procedures for disseminating the clinical intervention style of motivational interviewing (MI). MI was selected because (1) there is strong evidence of its efficacy in addressing substance use disorders, (2) its procedures are well specified, (3) it is consonant with current trends in managed care, and (4) it has many of the attributes specified by Everett Rogers as promoting adoption of an innovation into established practice. A pilot study showed that a 2-day workshop alone was insufficient to change counselors' practice behavior enough to make a difference for clients. Two promising training enhancement procedures (individualized feedback to clinicians, and reinforced practice through individual consultations) will be evaluated via a design combining between-group and within-group effects with 140 substance abuse practitioners. Two well-developed systems for process coding of tapes will be used both to evaluate the efficacy of training, and to advance theory-relevant knowledge of active processes operating in motivational interviewing. A parallel substudy will implement and evaluate MI training of Spanish-speaking clinicians.